EF Saving changes suddenly stopped working

Question

SaveChanges() on my EFv4 POCO context suddenly stopped working. It issues an error "Cannot insert NULL value into column 'postalcode' of table Clients"

Client entity contains a reference to PostCode (properties postalcode, postname) entity. PostCode reference is not null and so aren't it's properties. My Client entity is referenced from the Document entity.

Here's the code

    public void Add(Document instance)
    {
        // Firm reference
        instance.Firm =
         (from f in _ctx.Firms
            where f.firm_id.Equals(AppState.FirmId)
            select f).First();

        // Client reference (lazy loading is in place and works)
        if (instance.client_id != null)
            instance.Client = (from c in _ctx.Clients
                                                 where c.client_id.Equals(instance.client_id)
                                                 select c).First();

        instance.document_id = Guid.NewGuid();
        _ctx.Documents.AddObject(instance);
        _ctx.Documents.SaveChanges();
    }

The thing is, AddObject() works but SaveChanges() fails. I've inspected the Document instance, Client reference and Client's PostCode reference all over and through, all the values are there (which also proves that lazyloading is in place and working) but save doesn't happen.

Looking for ideas what could I've missed..

Answer 1

Firstly, you get the error when you run SaveChanges because that is when it tries to write to the database. Before then it is just in memory.

The error is that postalcode does not allow nulls.

My guess is that in a previous version of the model nulls were allowed. So there are some records without postal codes.

Alternatively, when you retrieve the client the postalcodes are not being retrieved.

In both cases the result is that you are trying to save a postalcode with value null.